Apparatus for supervising the functioning of an analog plural-channel regulating system

ABSTRACT

The mean value of the amplitude of analog signals appearing on individual control paths is continuously formed. Three-level switch means are provided which are addressed by groups of two control path voltages of the individual control paths, and a disturbed control path is disconnected by the switch means, and either the output signal of the mean-value forming unit or one of the remaining connected input signals is weighted, so that failure of one control path does not significantly affect the output signal of the mean-value forming unit which is supplied to following apparatus. Thus, the failure of a control path can occur without interruption or significantly changing the operation of this supervisory apparatus. This failure can sound an alarm which pinpoints the specific location of the fault.

United States Patent Waldmann [54] APPARATUS FOR SUPERVISING THEFUNCTIONING OF AN ANALOG PLURAL-CHANNEL REGULATING SYSTEM [72] Inventor:Hermann Waldmann, Wiesenstr. 14,

Weiher, Germany [22] Filed: April 21, 1971 [21] Appl. No.: 135,933

[30] Foreign Application Priority Data April 29, 1970 Germany ..P 20 20940.9

[52] US. Cl ..317/27 R, 307/204, 176/19 EC, 340/ 146.1 [51] Int. Cl..H02h 3/26 [58] Field of Search ..176/19, 19 EC, 20, 22, 24; 317/27 R;307/85, 86, 87, 204, 219; 340/ 146.1; 328/92 [56] References CitedUNITED STATES PATENTS 3,544,778 12/1970 Masters .....307/2l9 [451 Sept.5, 1972 FOREIGN PATENTS OR APPLICATIONS Primary Examiner-J. D. MillerAssistant Examiner-Harvey Fendelman Attorney-Curt M. Avery, Arthur E.Wilfond, Herbert L. Lerner and Daniel J. Tick Germany [5 7] ABSTRACT Themean value of the amplitude of analog signals appearing on individualcontrol paths is continuously formed. Three-level switch means areprovided which are addressed by groups of two control path voltages ofthe individual control paths, and a disturbed control path isdisconnected by the switch means, and either the output signal of themean-value forming unit or one of the remaining connected input signalsis weighted, so that failure of one control path does not significantlyafiect the output signal of the mean-value forming unit which issupplied to following apparatus. Thus, the failure of a control path canoccur without interruption or significantly changing the operation ofthis supervisory apparatus. This failure can sound an alarm whichpinpoints the specific location of the fault.

9Claims,5DrawingFigurcs APPARATUS FOR SUPERVISING THE FUNCTIONING OF ANANALOG PLURAL- CHANNEL REGULATING SYSTEM My invention concerns anapparatus for supervising the functioning of the individual controlpaths of an analog, plural-channel regulating system, and used, forinstance, in the control of nuclear reactors.

A supervisory apparatus of this kind has been published as GermanProvisional Pat. DAS) 1,280,431. Of the signals appearing on threecontrol paths, only the largest of these signals, at any one time,influences a positioning member through a maximumselection process,while the signals of the other two control paths are merely carried forcomparison purposes. A disadvantage of this method is that due to thismaximum-selection process, the time-averaged mean value of the amplitudeof the signal passing through the apparatus is, in principle, increasedrelative to the signals on the control paths in an undefmable manner ifthe signals are accompanied by harmonics or random, stochastic noisesignals. The considerable redundancy of this arrangement, which is dueto the fact that of three measuring or control systems, only one iseffective at any one time, is also unsatisfactory.

An object of my invention is to provide a more accurate supervisoryapparatus inserted directly in the paths of the signals supervised.

Another object of my invention is to provide a supervisory apparatuswhich, when a fault is sensed in one of the paths, produces an outputsignal for all the paths which is approximately the actual valuesthereof.

Still another object of my invention is to provide a supervisoryapparatus in which a fault in one of the control paths being superviseddoes not substantially affect the operation of the supervised paths.

Another object of my invention is to provide a supervisory apparatuswhich pinpoints the location of the fault.

Still another object of my invention is to provide a supervisoryapparatus which is less sensitive to harmonic and and other noisecarried on the control paths and which may cancel such noise when afault is detected.

Yet another object of my invention is to provide a supervisory apparatuswhich may be used to supervise any n number of control paths in a greatvariety of environments.

Other objects, advantages, and features of my invention will become moreapparent from the following description.

In accordance with the principles of my invention, the above objects areaccomplished by providing a supervisory apparatus havingtwo-out-of-three selection, with continuous mutual comparison of theindividual control paths and undisturbed transmission of the analogsignal in the event of failure of one control path. In particular, allcontrol paths are fed disconnectibly to the inputs of a mean-valueforming unit. Three-level switches are always connected with two controlpaths and actuate switching means for disconnecting one control pathfrom the input of the mean-value forming unit and for simultaneouslychanging the weighting of either its output signal or of one of itsinput signals supplied by the remaining control paths. In this manner,all path signals contribute uniformly to the formation of the signal tobe processed after it passes through the supervisory apparatus, and thetime-averaged mean value of the signal to be processed is not changedrelative to the individual measurement quantities on the control paths.Furthermore, there is the possibility that random, stochastic noisesignals may mutually be cancelled in the signal to be further processedor at least attenuate each other.

The invention will be further described with reference to embodimentsthereof, illustrated by way of example in the accompanying drawings inwhich:

FIG. 1 is a schematic diagram of an embodiment of the two-out-of-threeselection process of the supervisory apparatus of my invention;

FIG. 2 is another embodiment of the supervisory apparatus of myinvention;

FIG. 3 is a block diagram in which the supervisory apparatus of myinvention is utilized;

FIG. 4 is a schematic diagram of another embodiment in which thesupervisory apparatus of my invention may be utilized; and

FIG. 5 is a schematic diagram of a threshold level director used withthe supervisory apparatus of my invention.

Referring to FIG. 1, the input terminals 11, 12 and 13 of a supervisoryapparatus, in accordance with my invention, designated KK( control andcorrection unit) and to practical advantage combined in one module, areconnected with three paths S1, S2 and S3 of a three-channel controlsystem. The paths can originate in preceding elements of the controlsystem, not shown in detail, such as actual and preset-valuetransmitters, control amplifiers or other signal transmission devices.

Terminals 11 and 12 are connected with the inputs of a three-levelswitch 14, at the output of which there appears an output signalactuating a relay A, if the difference of the voltages appearing at theterminals 11 and 12 exceeds a small, presettable threshold value.Terminals 12, 13 and 11, 13, respectively, are connected with theadditional three-level switches 15 and 16 to energize the coils of therelays B and C, respectively, in a similar manner.

The position of the contacts designated a, b and c of the relays A, Band C shown in FIG. lis that occupied in the unenergized state of theserelays, which state exists if none of the three paths is disturbed, andtherefore, all the voltage differences appearing between the terminalsl1, l2 and 13 are below the threshold value. The voltages appearing onthe individual control paths S1, S2 and S3 are then approximately equal.In this condition, terminal 11 is connected via a double-throw contactc,terminal 12 via a double-throw contact b and terminal 13 via a furtherdouble-throw contact 0 with input resistors 3R of an operationalamplifier 17. The amplifier 17 in an unloaded condition has a very largegain and has a negative feedback via a resistor R, the resistance valueof which is one-third of that of each of the input resistors 3R of theoperational amplifier. The operational amplifier 17, thus, functions asa meanvalue forming unit inasmuch as the arithmetic mean of the voltagesapplied to its input resistors 3R appears at its input terminal 18. Ifall the control paths are undisturbed, the voltage appearing at theoutput terminal 18 practically corresponds to each of the individualcontrol path voltages.

To illustrate my invention, it will be assumed that, for instance, thevoltage appearing on the control path S1 is disturbed and, therefore,shows a considerable difference relative to the voltages appearing onthe control paths S2 and S3. In this event, the threshold alarms 14 and16 respond and actuate the relays A and C. The voltages at the terminals12 and 13 would now be connected via the double-throw contacts a and bwith the input resistors 3R of the operational amplifier 17, while theinput previously connected with the terminal 11 of the operationalamplifier I7 is disconnectd therefrom and is now connected to theterminal 12. The voltage which exists at the terminal 12 thus also feedsthe operational amplifier 17. Therefore, in forming the mean value inthe operational amplifier 17, the input signal of terminal 12 carriestwice the weight as that of terminal 13. The output signal at theterminal 18 therefore remains unaffected by the disengagement or faulton the disturbed path S1.

A signal lamp Ll may be connected to an external voltage U supplied froma terminal 19, via two make contacts of the relays A and C which areactuated in case of a disturbance in the path S1. As in most cases,several of the control and correction units KK shown in FIG. 1 are usedwithin one control system, it is desirable to provide one signal lamp Lat a central point which is assigned to all such supervisoryarrangements and would be connected with the terminal designated 20 ofsuch an apparatus. The make contacts of all existing alarm relays wouldtherefore be connected in parallel between this terminal 20 and therespective reference potential terminals 21, so that voltage is appliedto the central signal lamp L even if only one of the relays A, B or C inthe individual supervisory units KK pulls up. In a properly respondingsupervisory apparatus, the central signal lamp L, as well as two of thelamps assigned to the respective supervisory unit KK, will light.

The two-out-of-three selection process described above takes place in acorresponding manner in the event of disturbances in the control pathsS2 or S3. A disturbance in the path S2 would result in the operation ofthe relays A and B, and a disturbance in the path S3 in the operation ofrelays B and C. It is possible to realize the relays shown in FIG. 1 orthe functions of the contacts designated a, b and c by digital,electronically operating switching elements by using the well-knownrules of Boolean algebra. As a further modification of the arrangementshown in FIG. 1, the alarm device shown in FIG. 1 in the form of thecentral lamp L may consist of an alarm relay which is actuated, in orderto enhance the operating reliability, not by the parallelconnected makecontacts of the relays A to C but serially connected break contacts ofthese relays (holding current principle). The operational reliability ofthe installation can thereby be increased further.

In FIG. 2, another embodiment of the supervisory apparatus according tomy invention is shown, which realizes the principle of mean-valueformation with uniform participation of all control path voltages actingon the mean-value forming unit also for the disturbed case. For elementsof similar function, the corresponding reference symbols of FIG. 1 areretained. The threshold indicators 14 to 16, as well as the relays A toC, are energized in exactly the same manner as in the arrangement shownin FIG. 1. The circuit part related to the fault indication has beensubstantially retained and a horn designated H may also be used as thecentral warning device.

In the undisturbed case, in FIG. 2, all relays A, B and C areunenergized and the corresponding break contacts a, b and c are closed.In the negative feedback circuit of amplifier 17, only the feedbackresistor designated R is therefore effective. At the output terminal 18of the amplifier there appears the sum, multiplied by the factor US, ofthe three input voltages applied to the terminals ll, 12 and 13. Thepart of the negative feedback path that is bridged by a series-parallelarrangement of contacts a to b has a resistance R/2, exactly half theresistance of the resistor R. Therefore, the sum of the input voltagesoriginating in the two undisturbed control paths is multiplied by theoperational amplifier by a factor of /2 through the opening of the breakcontact a, c, a, b or b, c and is passed on to the output terminal 18. Adifferent weighting of the output signal of the mean-value forming unit,therefore, is accomplished relative to the sum of its input signals.

The essential difference of FIG. 2 re the arrangement of FIG. 1 consistsin that the path voltages to be connected to the input terminals 11, 12and 13 are fed, via the parallel circuit of break contacts, to the inputresistors of those two relays, which respond in case of a disturbance inthe path in question, and that by a seriesparallel circuit of furtherbreak contacts of these relays, the negative feedback resistance of theoperational amplifier 17 is, in part, varied in such a manner, that upondisconnecting one control path from the input of the amplifier, the gainof the latter increases by a factor of 3/2 relative to the undisturbedcondition.

In the variant according to FIG. 2, it becomes clear how thetwo-out-of-three selection monitoring circuit could readily be expandedto a three-out-of-four selection monitoring circuit or, generally, to anN-l )-0utof-nselection monitoring circuit. For a three-out-offourselection process, a total of six or in general, n( n- 1) k) three-levelswitches would be required for any possible combination of two pathvoltages, and break contacts of the respective three or in general, nl)relays that can be influenced by a path voltage would have to beconnected in parallel in the input and negative feedback circuit of theoperational amplifier 17 in a manner analogous to FIG. 2. The inputresistor and the parts of the negative feedback resistance that can andcannot be bridged would have the ratio 4 l ,4; or in general n l l/n -lAlthough a three-out-of-four system offers a higher degree ofreliability than the twoout-of-three system, it is substantially moreexpensive, so that it appears that its use would be limited, forexample, to the field of reactor technology.

The function-supervising apparatus according to my invention could beused in a control system with three paths in such a manner that threeoutput signals of the mutually corresponding control circuit elements inthe three control paths are controlled or corrected by only onemonitoring arrangement, and the output signal of the latter is fed inparallel to the inputs of three following, signal-processing controlcircuit elements. With this arrangement, however, the supervisoryfunction according to the two-out-of-three selection process would notinclude the control and correction members themselves because with suchan arrangement, the separation of the three-channels of the controlsystem would be violated. It is therefore practically advantageous toprovide a control and correction circuit for each signal-processingcontrol circuit element, so that three correction circuits are alwaysaddressed in parallel by the output of a control circuit element.

FIG. 3 shows the schematic diagram of such an arrangement. The outputquantities 1.1, 1.2, and 1.3 of three similarly constructed referencevalue transmitters are processed by a remote-transmission arrangement 2into the output signals 2.1, 2.2 and 2.3 which address three control andcorrection members KK according to FIG. 1 or FIG. 2. The outputs 3.1,3.2 and 3.3 act as reference values for three mixers designated 6, towhich are fed output quantities 5.1, 5.2 and 5.3 of further functionsupervising units KK which are fed in an analogous manner by threeactual-value transmitters designated 4. In order to monitor the controlsystem sections following the mixers 6 and controls 8, three furthersupervisory units KK are respectively provided which at their inputs areconnected in a corresponding manner with the outputs of the controlsystem elements preceding them. The system shown in FIG. 3 permitscontinuous supervision and simple and unambiguous fault location, as theoccurrence of trouble is reported by the central warning device and thetrouble location can be determined by the signal lamps L1 to L3 assignedto the individual sections of the control circuit.

The monitoring of controls with an integrator, operating in parallel,could present problems, since it is possible that three mutuallyindependent integrating controls could assume different output voltagesdue to unavoidable tolerances in the formation of the signal deviationand with respect to the operating point of the integrator. Therefore,monitoring circuits assigned to the integrators would respondunintentionally even if they otherwise function properly.

The circuit shown in FIG. 4 prevents this situation by letting each ofthe integrating controls 22, 23 and 24 arranged in the three controlledsystems provide, by means of a negative feedback resistor R, connectedwith the input of the correction and supervisory circuit KK a staticcondition, which is normally fully compensated by positive feedback fromthe output 18 of the mean-value forming unit via a resistor R,,, of thesame magnitude as R,, The mentioned tolerances in the signal deviationthen take effect only to the extent that the output voltages of thethree integrating controls 22 to 24 showing slight differences, whichcan be taken into account by suitable adjustment of the response limitsof the three-level switches in the control and correction circuits KK.In this manner, the output voltages of all integrating controls arematched to each other in the undisturbed condition, while supervision inthe case of a disturbance, for instance, in the event of a sudden,fault-connected rise of the output voltage of one control to the limitpoint, is assured in the manner described above.

An example of an embodiment of the three-level switch designated 14 to16 in FIGS. 1 and 2 is shown in FIG. 5. The switch consists of anoperational amplifier 25, the input terminals 26 and 26 of which are fedthe voltages to be compared with each other. The output of the amplifieris connected via a low-resistance potentiometer 28 to a referencepotential with the tap of the potentiometer connected to a negativefeedback resistor 29. The negative feedback resistor 29 as well as theother resistors connected with the amplifier inputs designated with +andare of the same magnitude. The amplifier output is connected via twoseries-connected diodes 30, for example, Zener diodes, with the input ofan amplifier 31 of such high gain that its output voltage practicallyassumes its maximum, either positive or negative, if the input voltageis different from zero. At a given difference, adjustably by thepotentiometer 28, of the voltages applied to the input terminals 26 and27, the breakdown voltage of one of the diodes 30 is exceeded, so thatthe output signal of the amplifier 31 suddenly jumps to its outputlimit. The functions indicated in the block diagram for the elements 14and 16 in FIGS. 1 and 2 can thus be achieved in this manner.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above apparatus withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description and shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

I claim:

1. Apparatus for supervising the operation of a plurality of controlpaths of an analog plural-channel regulation system and sensing afailure in one of said paths, comprising comparison means forcontinuously comparing the signal amplitudes on pairs of said pluralityof control paths, mean-value forming means for receiving said signalamplitudes as inputs and forming an output which is the mean of theinputs applied thereto, said output being at an output level without afailure on any of said paths, and switch means responsive to apredetermined difference between said compared pairs for disconnectingone of said control paths from said mean-value forming means andmaintaining the output of said mean-value forming means at approximatelythe output level when a failure occurs in one of said paths.

2. Apparatus as set forth in claim 1, wherein upon the occurrence of afailure in one of said paths, said switch means changes the weighting ofone of the inputs still connected to said mean-valve forming means.

3. Apparatus as set forth in claim 1, wherein upon the occurrence of afailure in one of said paths, said switch means changes the weighting ofthe output of said mean-value forming means.

4. Apparatus as set forth in claim 1, wherein said number of paths isthree and said apparatus operates in a two-out-of-three selection mode.

5. Apparatus as set forth in claim 3, wherein said mean-value formingmeans comprises an operational amplifier and a feedback resistor, saidswitching means changing the resistance of said feedback resistorresponsive to the occurrence of a fault in one of said paths.

6. Apparatus as set forth in claim 1, comprising a plurality of warningmeans with respective ones of said warning means associated withrespective ones of said plurality of paths, said one of said warningmeans being energized when a failure occurs in an associated controlpath.-

between said first and second operational amplifiers.

9. Apparatus as set forth in claim 1, comprising integrating memberswithin said control paths, the inputs of said mean-value forming meansbeing coupled through a negative feedback coupling to the input of anintegrating member, the output of said mean-value forming unit beingcoupled through a positive feedback coupling to the input of saidintegrating member.

1. Apparatus for supervising the operation of a plurality of control paths of an analog plural-channel regulation system and sensing a failure in one of said paths, comprising comparison means for continuously comparing the signal amplitudes on pairs of said plurality of control paths, mean-value forming means for receiving said signal amplitudes as inputs and forming an output which is the mean of the inputs applied thereto, said output being at an output level without a failure on any of said paths, and switch means responsive to a predetermined difference between said compared pairs for disconnecting one of said control paths from said mean-value forming means and maintaining the output of said mean-value forming means at approximately the output level when a failure occurs in one of said paths.
 2. Apparatus as set forth in claim 1, wherein upon the occurrence of a failure in one of said paths, said switch means changes the weighting of one of the inputs still connected to said mean-valve forming means.
 3. Apparatus as set forth in claim 1, wherein upon the occurrence of a failure in one of said paths, said switch means changes the weighting of the output of said mean-value forming means.
 4. Apparatus as set forth in claim 1, wherein said number of paths is three and said apparatus operates in a two-out-of-three selection mode.
 5. Apparatus as set forth in claim 3, wherein said mean-value forming means comprises an operational amplifier and a feedback resistor, said switching means changing the resistance of said feedback resistor responsive to the occurrence of a fault in one of said paths.
 6. Apparatus as set forth in claim 1, comprising a plurality of warning means with respective ones of said warning means associated with respective ones of said plurality of paths, said one of said warning means being energized when a failure occurs in an associated control path.
 7. Apparatus as set forth in claim 6, comprising a central warning means being energized when a failure occurs on any of said plurality of paths.
 8. Apparatus as set forth in claim 1, wherein said comparison means comprises a first operational amplifier having two inputs connected with respective ones of said pairs of control paths and a variable feedback resistance for varying the gain of said operational amplifier, Zener diode means and a second operational amplifier, said Zener diode means connected in series between said first and second operational amplifiers.
 9. Apparatus as set forth in claim 1, comprising integrating members within said control paths, the inputs of said mean-value forming means being coupled through a negative feedback coupling to the input of an integrating member, the output of said mean-value forming unit being coupled through a positive feedback coupling to the input of said integrating member. 